Lithium-ion battery and apparatus

ABSTRACT

The present application provides a lithium-ion battery and an apparatus, the lithium-ion battery includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separation film. The positive active material in the positive electrode sheet includes Li x1 Co y1 M 1-y1  O 2-z1 Q z1 , 0.5≤x1≤1.2, 0.8≤y1&lt;1.0, 0≤z1≤0.1, and M is selected from one of Al, Ti, Zr, Y, and Mg, and Q is selected from one or more of F, Cl, and S. The electrolyte contains an additive A and an additive B, the additive A is a polynitrile six-membered nitrogen-heterocyclic compound with a relatively low oxidation potential, and the additive B is an aliphatic dinitrile or polynitrile compound with a relatively high oxidation potential. The lithium-ion battery of the present application has superb cycle performance and storage performance, especially under high-temperature and high-voltage conditions.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of International ApplicationNo. PCT/CN2019/125325, filed on Dec. 13, 2019, which claims priority toChinese Patent Application No. 201811537016.0, filed on Dec. 14, 2018,both of which are hereby incorporated by reference in their entireties.

TECHNICAL FIELD

The present application relates to the field of energy storagematerials, and in particular, to a lithium-ion battery and an apparatus.

BACKGROUND

Lithium-ion batteries are widely applied to electromobiles and consumerelectronic products due to their advantages such as high energy density,high output power, long cycle life and low environmental pollution.Current requirements on lithium-ion batteries are high voltage, highpower, long cycle life, long storage life and superb safety performance.

Currently, LiCoO₂ is widely used as a positive active material inlithium-ion batteries and shows relatively stable performance duringcycling between fully discharged LiCoO₂ and semi-charged Li_(0.5)CoO₂(4.2 V vs. Li). Therefore, lithium ions that are actually used accountonly for ½ of lithium ions actually contained in LiCoO₂. When thevoltage is greater than 4.2 V, the remaining ½ of lithium ions containedin LiCoO₂ may continue to be extracted. However, during deepdelithiation, Co³⁺ is oxidized into quite unstable Co⁴⁺, which oxidizesan electrolyte together with surface oxygen that loses a large quantityof electrons. In this case, a large amount of gas is produced inside thebatteries, causing the batteries to swell. In addition, due to acorrosive effect of HF in the electrolyte on a surface of a positiveelectrode, Co⁴⁺ is dissolved in the electrolyte and deposited on asurface of a negative electrode, catalyzing reduction of theelectrolyte, and also producing a large amount of gas that causes thebatteries to swell. In addition, due to high overlapping between a 3denergy level of Co and a 2p energy level of O, the deep delithiationalso causes lattice oxygen to lose a large quantity of electrons,resulting in sharp shrinkage of LiCoO₂ unit cells along a c-axisdirection, and leading to instability or even collapse of a local bulkstructure. This eventually causes loss of LiCoO₂ active sites, and arapid decrease in capacity of the lithium-ion batteries. Therefore,LiCoO₂ has very poor performance when being used in a high-voltagesystem greater than 4.2 V.

In view of this, the present application is hereby proposed.

SUMMARY

In view of the problems in the background, an object of the presentapplication is to provide a lithium-ion battery and an apparatus. Thelithium-ion battery has superb cycle performance and storageperformance, especially under high-temperature and high-voltageconditions.

In order to achieve the abovementioned object, in a first aspect, thepresent application provides a lithium-ion battery, including anelectrode assembly and an electrolyte. The electrode assembly includes apositive electrode sheet, a negative electrode sheet, and a separationfilm. A positive active material of the positive electrode sheetincludes Li_(x1)Co_(y1)M_(1-y1)O_(2-z1)Q_(z1), where 0.5≤x1≤1.2,0.8≤y1<1.0, 0≤z1≤0.1, M is selected from one or more of Al, Ti, Zr, Y,and Mg, Q is selected from one or more of F, Cl and S. The electrolytecontains an additive A and an additive B. The additive A is selectedfrom one or more of compounds represented by Formula I-1, Formula I-2,and Formula I-3, and the additive B is selected from one or more ofcompounds represented by Formula II-1 and Formula II-2.

In the Formula I-1, the Formula I-2, and the Formula I-3: R₁, R₂, R₃,and R₄ each are independently selected from a hydrogen atom, a halogenatom, a substituted or unsubstituted C₁-C₁₂ alkyl group, a substitutedor unsubstituted C₁-C₁₂ alkoxy group, a substituted or unsubstitutedC₁-C₁₂ amine group, a substituted or unsubstituted C₂-C₁₂ alkenyl group,a substituted or unsubstituted C₂-C₁₂ alkynyl group, a substituted orunsubstituted C₆-C₂₆ aryl group, a substituted or unsubstituted C₂-C₁₂heterocyclic group, where a substituent group is selected from one ormore of a halogen atom, a nitrile group, a C1-C6 alkyl group, a C₂-C₆alkenyl group, a C₁-C₆ alkoxy group; x, y, and z each are independentlyselected from integers 0-8; and m, n, and k each are independentlyselected from integers 0-2.

In the Formula II-1 and Formula II-2: R₅ is selected from a substitutedor unsubstituted C₁-C₁₂ alkylene group, a substituted or unsubstitutedC₂-C₁₂ alkenylene group, a substituted or unsubstituted C₂-C₁₂alkynylene group, R₆, R₇, and R₈ each are independently selected fromsubstituted or unsubstituted C₀-C₁₂ alkylene group, substituted orunsubstituted C₂-C₁₂ alkenylene group, substituted or unsubstitutedC₂-C₁₂ alkynylene group, where the substituent group is selected fromone or more of a halogen atom, a nitrile group, a C₁-C₆ alkyl group, aC₂-C₆ alkenyl group, and a C₁-C₆ alkoxy group.

In a second aspect in of the present application, the presentapplication provides an apparatus, including the lithium-ion batterydescribed in the first aspect of the present application.

Compared with the prior art, the present application includes at leastthe following beneficial effects:

In the present application, a positive active material that contains ametal ion M-doped lithium cobalt oxide materialLi_(x1)Co_(y1)M_(1-y1)O_(2-z1)Q_(z1) is used, where the doping element Mserves as a framework in the lithium cobalt oxide material. This couldreduce lattice deformation of the lithium cobalt oxide material duringdeep delithiation, delay degradation of bulk structure of the lithiumcobalt oxide material, and improve structural stability of thelithium-ion battery when the lithium-ion battery is used at a highvoltage greater than 4.2 V.

The electrolyte of the present application includes a combined additiveof the additive A and the additive B. The additive A is a polynitrilesix-membered nitrogen-heterocyclic compound with a relatively lowoxidation potential, such that a stable complex layer can be formed on asurface of the positive active material during formation of the battery.This could effectively passivate the surface of the positive activematerial and inhibit its oxidation effect on the electrolyte, and reducegas production of the battery; the electrolyte of the presentapplication further includes aliphatic dinitrile or polynitrilecompounds with a relatively high oxidation potential, which can stablyexist in the electrolyte for a long time, and can repair the damagedcomplex layer at any time during cycling or high-temperature storage,reduce dissolution of transition metal ions, and greatly reduce damageof the transition metal to the SEI film deposited on the negativeelectrode after dissolution; therefore, the electrolyte of the presentapplication can improve the cycle performance and storage performance oflithium-ion batteries, especially improve the cycle performance andstorage performance of lithium-ion batteries under of high-temperatureand high-voltage conditions. The apparatus of the present applicationincludes the lithium-ion battery described in the first aspect of thepresent application, and therefore provides at least the same advantagesas the lithium-ion battery.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a carbon nuclear magnetic resonance spectrum of a compound A1.

FIG. 2 is a carbon nuclear magnetic resonance spectrum of a compound A2.

FIG. 3 is a carbon nuclear magnetic resonance spectrum of a compound A3.

FIG. 4 is a schematic diagram of an embodiment of a lithium-ion battery.

FIG. 5 is a schematic diagram of an embodiment of a battery module.

FIG. 6 is a schematic diagram of an embodiment of a battery pack;

FIG. 7 is an exploded diagram of FIG. 6.

FIG. 8 is a schematic diagram of an embodiment of an apparatus using alithium-ion battery as a power source.

DETAILED DESCRIPTION OF EMBODIMENTS

A lithium-ion battery and an apparatus according to the presentapplication are described in detail below.

First, the lithium-ion battery according to the first aspect of thepresent application is described.

The lithium-ion battery according to the present application includes anelectrode assembly and an electrolyte. The electrode assembly includes apositive electrode sheet, a negative electrode sheet, and a separationfilm.

Where, a positive active material in the positive electrode sheetincludes Li_(x1)Co_(y1)M_(1-y1)O_(2-z1)Q_(z1), where 0.5≤x1≤1.2,0.8≤y1<1.0, 0≤z1≤0.1, M is selected from one or more of Al, Ti, Zr, Y,and Mg, and Q is selected from one or more of F, Cl, and S. Theelectrolyte includes an additive A and an additive B, the additive A isselected from one or more of compounds represented by Formula I-1,Formula I-2 and Formula I-3, and the additive B is selected from one ormore of compounds represented by Formula II-1 and Formula II-2.

In the Formula I-1, the Formula I-2, and the Formula I-3: R₁, R₂, R₃,and R₄ each are independently selected from a hydrogen atom, a halogenatom, substituted or a unsubstituted C₁-C₁₂ alkyl group, a substitutedor unsubstituted C₁-C₁₂ alkoxy group, a substituted or unsubstitutedC₁-C₁₂ amine group, a substituted or unsubstituted C₂-C₁₂ alkenyl group,a substituted or unsubstituted C₂-C₁₂ alkynyl group, a substituted orunsubstituted C₆-C₂₆ aryl group, a substituted or unsubstituted C₂-C₁₂heterocyclic group, where a substituent group (indicating a substitutioncase in the “substituted or unsubstituted” herein) is selected from oneor more of a halogen atom, a nitrile group, a C₁-C₆ alkyl group, a C₂-C₆alkenyl group and a C₁-C₆ alkoxy group; x, y, and z each areindependently selected from integers 0-8; and m, n, and k each areindependently selected from integers 0-2.

In the Formula II-1 and the Formula II-2: R₅ is selected from asubstituted or unsubstituted C₁-C₁₂ alkylene group, a substituted orunsubstituted C₂-C₁₂ alkenylene group, a substituted or unsubstitutedC₂-C₁₂ alkynylene group, R₆, R₇, and R₈ each are independently selectedfrom a substituted or unsubstituted C₀-C₁₂ alkylene group, a substitutedor unsubstituted C₂-C₁₂ alkenylene group, a substituted or unsubstitutedC₂-C₁₂ alkynylene group, where the substituent group (indicating asubstitution case in the “substituted or unsubstituted” herein) isselected from one or more of a halogen atom, a nitrile group, a C₁-C₆alkyl group, a C₂-C₆ alkenyl group, and a C₁-C₆ alkoxy group.

The lithium-ion battery of the present application has superb cycleperformance and storage performance, especially under high-temperatureand high-voltage conditions. On the one hand, in the presentapplication, a positive active material that contains a metal ionM-doped lithium cobalt oxide materialLi_(x1)Co_(y1)M_(1-y1)O_(2-z1)Q_(z1) is used, where the doping element Mserves as a framework in the lithium cobalt oxide material. This couldreduce lattice deformation of the lithium cobalt oxide material duringdeep delithiation, delay degradation of bulk structure of the lithiumcobalt oxide material, and improve structural stability of thelithium-ion battery when the lithium-ion battery is used at a highvoltage greater than 4.2 V. On the other hand, the additive A and theadditive B are added into the electrolyte of the present application atthe same time, and the two can play a synergistic effect to protect thelithium-ion battery together, and make the lithium-ion battery havesuperb cycle performance and storage performance, especially underhigh-temperature and high-voltage conditions.

Specifically:

the additive A is a polynitrile six-membered nitrogen-heterocycliccompound with a relatively low oxidation potential. Nitrogen atoms inthe nitrile groups contain lone pair electrons, which have relativelystrong complexation with a transition metal in the positive activematerial. After being applied in the electrolyte, the additive A may beadsorbed on a surface of the positive active material during formationof the battery to form a loose porous protective film during theformation of the battery and effectively passivate the surface of thepositive active material. The porous protective film can not onlyisolate the surface of the positive active material from direct contactwith the electrolyte without affecting the normal transmission of ions,but also can reduce the surface activity of the positive active materialwhile inhibiting a large number of side reactions on the surface of thepositive active material, thereby achieving the effect of decreasingside reaction products and reducing gas production.

The additive A has a special six-membered nitrogen-heterocyclicstructure. A spacing between nitrile groups is closer to that betweentransition metals on the surface of the positive active material. Thiscould maximize complexation of the nitrile groups and allow more nitrilegroups to have a complexation effect. Therefore, compared with aconventional linear nitrile compound, the polynitrile six-memberednitrogen-heterocyclic compound in the present application has a betterpassivation effect.

The special six-membered nitrogen-heterocyclic structure of the additiveA in this application can further lower an oxidation potential ofmolecules, so that a stable complex layer may be formed on the surfaceof the positive active material during formation of the battery. Thismay help improve electrochemical performance of an entire batterysystem, for example, by reducing gas production and extending a cyclelife under high-temperature and high-voltage conditions.

The additive B is an aliphatic dinitrile or polynitrile compound. Analiphatic framework has strong oxidation resistance and can exist stablyfor a long time after being added to the electrolyte. Nitrogen atoms inthe nitrile groups contain lone pair electrons, which have relativelystrong complexation with a transition metal in the positive activematerial, and can repair the damaged complex layer (formed by theadditive A) at any time during cycling or high-temperature storage,reduce dissolution of transition metal ions, and greatly reduce thedamage of the transition metal to the SEI film deposited on the negativeelectrode after dissolution. Therefore, when the additive B is appliedto the electrolyte, the lithium-ion battery has superb high temperatureand high voltage cycle performance and storage performance.

In the lithium-ion battery of this application, preferably, based ontotal mass of the electrolyte, mass percent of the additive A is0.1%-10%. If the amount of the additive A is too low, improvement madeby the additive A to the electrolyte is not obvious; if the amount ofthe additive A is too high, the complex layer formed by the additive Abeing adsorbed on the surface of the positive active material would betoo thick and dense, affecting diffusion and migration of lithium ions,and greatly increasing positive electrode impedance. In addition,excessively high amount of the additive A further causes an increase inoverall viscosity of the electrolyte and a decrease in an ionicconductivity, and therefore, affects performance of the lithium-ionbattery. An upper limit of the amount of the additive A may be any oneselected from 10%, 9%, 8%, 7%, 6%, 5%, 4.5%, 4%, 3.5%, 3%, 2.5%, 2%,1.5%, 1%, or 0.8%, and a lower limit of the amount of the additive A maybe any one selected from 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%,0.9%, 1.0%, or 1.2%.

Even more preferably, based on the total mass of the electrolyte, themass percent of the additive A is 0.1%-3.5%.

In the lithium-ion battery of this application, preferably, based ontotal mass of the electrolyte, mass percent of the additive B is0.1%-10%. If an amount of the additive B is too low, the repairingeffect on the complex layer formed by the additive A is not obvious; ifthe amount of the additive B is too high, the complex layer formed onthe surface of the positive active material is too thick and too dense,which greatly increase impedance of the negative electrode, andadversely affects the performance of the lithium-ion battery. An upperlimit of the amount of the additive B may be selected from any one of10%, 9%, 8%, 7%, 6%, 5%, 4.5%, 4%, 3.5%, 3%, 2.5%, 2%, 1.5%, 1%, 0.8%,and a lower limit of the amount of the additive B may be selected fromany one of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%.

Even more preferably, based on the total mass of the electrolyte, themass percent of the additive B is 0.1% to 5%.

In the lithium-ion battery of the present application, in the compoundsrepresented by the Formula I-1, the Formula I-2, and the Formula I-3:

the C₁-C₁₂ alkyl group can be a chain alkyl group or a cyclic alkylgroup. The chain alkyl group may be a straight chain alkyl group or abranched chain alkyl group, and hydrogen on a ring of the cyclic alkylgroup may be further substituted by an alkyl group. A preferable lowerlimit of a quantity of carbon atoms in the C₁-C₁₂ alkyl group is 1, 2,3, 4, and 5, and a preferable upper limit is 3, 4, 5, 6, 8, 10, or 12.Preferably, a C₁-C₁₀ alkyl group is selected. More preferably, a C₁-C₆chain alkyl group, or a C₃-C₈ cyclic alkyl group is selected.Furthermore preferably, a C₁-C₄ chain alkyl group, or a C₅-C₇ cyclicalkyl group is selected. Examples of the C₁-C₁₂ alkyl group mayspecifically include a methyl group, an ethyl group, an n-propyl group,isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group,a tert-butyl group, an n-pentyl group, an isopentyl group, a neopentylgroup, a hexyl group, a 2-methyl-pentyl group, a 3-methyl-pentyl group,a 1,1,2-trimethyl-propyl group, a 3,3-dimethyl-butyl group, a heptylgroup, a 2-heptyl group, a 3-heptyl group, a 2-methylhexyl group, a3-methylhexyl group, an isoheptyl group, an octyl group, a nonyl group,and a decyl group.

When the aforementioned C₁-C₁₂ alkyl group contains oxygen atoms, theC₁-C₁₂ alkyl group may be a C₁-C₁₂ alkoxy group. Preferably, a C₁-C₁₀alkoxy group is selected. More preferably, a C₁-C₆ alkoxy group isselected. Furthermore preferably, a C₁-C₄ alkoxy group is selected.Examples of the C₁-C₁₂ alkoxy group may specifically include a methoxygroup, an ethoxy group, an n-propoxy group, an isopropoxy group, ann-butoxy group, a sec-butoxy group, a t-butoxy group, an n-pentyloxygroup, an isopentyloxy group, a cyclopentyloxy group, and acyclohexyloxy group.

The C₂-C₁₂ alkenyl group may be a cyclic alkenyl group or a chainalkenyl group, and the chain alkenyl group may be a linear alkenyl groupor a branched alkenyl group. In addition, preferably, the C₂-C₁₂ alkenylgroup has one double bond. A preferred lower limit of the quantity ofcarbon atoms in the C₂-C₁₂ alkenyl group is 2, 3, 4, or 5, and apreferred upper limit is 3, 4, 5, 6, 8, 10, or 12. Preferably, a C₂-C₁₀alkenyl group is selected. More preferably, a C₂-C₆ alkenyl group isselected. Furthermore preferably, a C₂-C₅ alkenyl group is selected.Examples of the C₂-C₁₂ alkenyl group may specifically include a vinylgroup, an allyl group, an isopropenyl group, a pentenyl group, acyclohexenyl group, a cycloheptenyl group, and a cyclooctenyl group.

The C₂-C₁₂ alkynyl group may be a cyclic alkynyl group or a chainalkynyl group, and the chain alkynyl group may be a linear alkynyl groupor a branched alkynyl group. In addition, preferably, the C₂-C₁₂ alkynylgroup has one triple bond. A preferred lower limit of the quantity ofcarbon atoms in the C₂-C₁₂ alkynyl group is 2, 3, 4, or 5, and apreferred upper limit is 3, 4, 5, 6, 8, 10, or 12. Preferably, a C₂-C₁₀alkynyl group is selected. More preferably, a C₂-C₆ alkynyl group isselected. Furthermore preferably, a C₂-C₅ alkynyl group is selected.Examples of the C₂-C₁₂ alkynyl group may specifically include an ethynylgroup, a propargyl group, an isopropynyl group, a pentynyl group, acyclohexynyl group, a cycloheptynyl group, and a cyclooctynyl group.

The C₁-C₁₂ amine group may be selected from

where R′ and R″ are selected from the C₁-C₁₂ alkyl group.

The C₆-C₂₆ aryl group may be a phenyl group, a phenylalkyl group, abiphenyl group, or a fused ring aromatic hydrocarbon group (for example,a naphthyl group, an anthracenyl group, or a phenanthrenyl group). Thebiphenyl group and the fused ring aromatic hydrocarbon group may befurther substituted with an alkyl group or an alkenyl group. Preferably,a C₆-C₁₆ aryl group is selected. More preferably, a C₆-C₁₄ aryl group isselected. Furthermore preferably, a C₆-C₉ aryl group is selected.Examples of the C₆-C₂₆ aryl group may specifically include a phenylgroup, a benzyl group, a biphenyl group, a p-tolyl group, an o-tolylgroup, an m-tolyl group, a naphthyl group, an anthracenyl group, and aphenanthryl group.

A hetero atom in the C₂-C₁₂ heterocyclic group may be selected from oneor more of oxygen, nitrogen, sulfur, phosphorus, and boron, and aheterocyclic ring may be an aliphatic heterocyclic ring or an aromaticheterocyclic ring. Preferably, a C₂-C₁₀ heterocyclic group is selected.More preferably, a C₂-C₇ heterocyclic group is selected. Furthermorepreferably, a five-membered aromatic heterocyclic ring, a six-memberedaromatic heterocyclic ring, and a benzo heterocyclic ring are selected.Examples of the C₂-C₁₂ heterocyclic group may specifically include anethylene oxide group, a propylene oxide group, an ethylene sulfidegroup, an aziridine group, a β-propiolactone group, a furyl group, athienyl group, a pyrrolyl group, a thiazolyl group, an imidazolyl group,a pyridyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinylgroup, an indolyl group, and a quinolinyl group.

The halogen atom used as a substituent group may be selected from one ormore of a fluorine atom, a chlorine atom, and a bromine atom.Preferably, the halogen atom is a fluorine atom.

(1) Specifically, the compound represented by the Formula I-1 is apolynitrile compound.

In the Formula I-1:

Preferably, R₁, R₂, R₃, and R₄ each are independently selected from ahydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, asubstituted or unsubstituted C₁-C₆ linear or branched alkyl group, asubstituted or unsubstituted C₅-C₉ cyclic alkyl group, a substituted orunsubstituted C₁-C₆ alkoxy group, a substituted or unsubstituted C₁-C₆amine group, a substituted or unsubstituted C₂-C₆ alkenyl group, asubstituted or unsubstituted C₂-C6 alkynyl group, a substituted orunsubstituted C₆-C₁₂ aryl group, or a substituted or unsubstitutedC₂-C₁₂ heterocyclic group. More preferably, R₁, R₂, R₃, and R₄ each areindependently selected from a hydrogen atom, a fluorine atom, a chlorineatom, a bromine atom, a substituted or unsubstituted C₁-C₃ linear orbranched alkyl group, a substituted or unsubstituted C₅-C₇ cyclic alkylgroup, a substituted or unsubstituted C₁-C₃ alkoxy group, a substitutedor unsubstituted C₁-C₃ amine group, a substituted or unsubstituted C₂-C₃alkenyl group, a substituted or unsubstituted C₂-C₃ alkynyl group, asubstituted or unsubstituted C₆-C₈ aryl group, or a substituted orunsubstituted C₂-C₇ heterocyclic group. The substituent group isselected from one or more of halogen atoms.

Preferably, x is selected from integers 0-6; more preferably, isselected from integers 0-4; furthermore preferably, is selected from 0,1, or 2.

Preferably, y is selected from integers 0-6; more preferably, isselected from integers 0-4; furthermore preferably, is selected from 0,1, or 2.

Preferably, m is selected from 1 or 2. Preferably, n is selected from 1or 2.

Preferably, R₁ and R₃ are same groups. More preferably, R₁, R₃, and R₄are all same groups.

Preferably, R₁ and R₃ are both hydrogen atoms. More preferably, R₁, R₃,and R₄ are all hydrogen atoms.

Preferably, R₁, R₂, R₃, and R₄ are all hydrogen atoms; or R₁, R₃, and R₄are all hydrogen atoms, and R₂ is selected from a fluorine atom, achlorine atom, a bromine atom, a substituted or unsubstituted C₁-C₆linear or branched alkyl group, or a substituted or unsubstituted C₁-C₆alkoxy group. The substituent group is selected from one or more ofhalogen atoms. Preferably, the substituent group is selected from afluorine atom.

Preferably, the compound represented by the Formula I-1 may bespecifically selected from one or more of the following compounds, butthe present application is not limited to thereto:

(2) Specifically, the compound represented by the Formula I-2 is apolynitrile piperazine compound.

In the Formula I-2:

Preferably, R₁, R₂, R₃, and R₄ each are independently selected from ahydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, asubstituted or unsubstituted C₁-C₆ linear or branched alkyl group, asubstituted or unsubstituted C₅-C₉ cyclic alkyl group, a substituted orunsubstituted C₁-C₆ alkoxy group, a substituted or unsubstituted C₁-C₆amine group, a substituted or unsubstituted C₂-C₆ alkenyl group, asubstituted or unsubstituted C₂-C6 alkynyl group, a substituted orunsubstituted C₆-C₁₂ aryl group, or a substituted or unsubstitutedC₂-C₁₂ heterocyclic group. More preferably, R₁, R₂, R₃, and R₄ each areindependently selected from a hydrogen atom, a fluorine atom, a chlorineatom, a bromine atom, a substituted or unsubstituted C₁-C₃ linear orbranched alkyl group, a substituted or unsubstituted C₅-C₇ cyclic alkylgroup, a substituted or unsubstituted C₁-C₃ alkoxy group, a substitutedor unsubstituted C₁-C₃ amine group, a substituted or unsubstituted C₂-C₃alkenyl group, a substituted or unsubstituted C₂-C₃ alkynyl group, asubstituted or unsubstituted C₆-C₈ aryl group, or a substituted orunsubstituted C₂-C₇ heterocyclic group. The substituent group isselected from one or more of halogen atoms.

Preferably, x is selected from integers 0-6; more preferably, isselected from integers 0-4; furthermore preferably, is selected from 0,1, or 2. Preferably, y is selected from integers 0-6; more preferably,is selected from integers 0-4; furthermore preferably, is selected from0, 1, or 2.

Preferably, m is selected from 1 or 2. Preferably, n is selected from 1or 2.

Preferably, at least two of R₁, R₂, R₃, and R₄ are same groups. Morepreferably, at least three of R₁, R₂, R₃, and R₄ are same groups.

Preferably, at least two of R₁, R₂, R₃, and R₄ are hydrogen atoms. Morepreferably, at least three of R₁, R₂, R₃, and R₄ are hydrogen atoms.

Preferably, R₁, R₂, R₃, and R₄ are all hydrogen atoms; or three of R₁,R₂, R₃, and R₄ are hydrogen atoms, and the remaining one is selectedfrom a fluorine atom, a chlorine atom, a bromine atom, a substituted orunsubstituted C₁-C₆ linear or branched alkyl group, or a substituted orunsubstituted C₁-C₆ alkoxy group. The substituent group is selected fromone or more of halogen atoms. Preferably, the substituent group isselected from a fluorine atom.

Preferably, the compound represented by the Formula I-2 may bespecifically selected from one or more of the following compounds, butthe present application is not limited thereto:

(3) Specifically, the compound represented by the Formula I-3 is apolynitrile s-triazine compound.

In the Formula I-3:

Preferably, R₁, R₂, and R₃ each are independently selected from ahydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, asubstituted or unsubstituted C₁-C₆ linear or branched alkyl group, asubstituted or unsubstituted C₅-C₉ cyclic alkyl group, a substituted orunsubstituted C₁-C₆ alkoxy group, a substituted or unsubstituted C₁-C₆amine group, a substituted or unsubstituted C₂-C₆ alkenyl group, asubstituted or unsubstituted C₂-C6 alkynyl group, a substituted orunsubstituted C₆-C₁₂ aryl group, or a substituted or unsubstitutedC₂-C₁₂ heterocyclic group. More preferably, R₁, R₂, and R₃ each areindependently selected from a hydrogen atom, a fluorine atom, a chlorineatom, a bromine atom, a substituted or unsubstituted C₁-C₃ linear orbranched alkyl group, a substituted or unsubstituted C₅-C₇ cyclic alkylgroup, a substituted or unsubstituted C₁-C₃ alkoxy group, a substitutedor unsubstituted C₁-C₃ amine group, a substituted or unsubstituted C₂-C₃alkenyl group, a substituted or unsubstituted C₂-C₃ alkynyl group, asubstituted or unsubstituted C₆-C₈ aryl group, or a substituted orunsubstituted C₂-C₇ heterocyclic group. The substituent group isselected from one or more of halogen atoms.

Preferably, x is selected from integers 0-6; more preferably, isselected from integers 0-4; furthermore preferably, is selected from 0,1, or 2. Preferably, y is selected from integers 0-6; more preferably,is selected from integers 0-4; furthermore preferably, is selected from0, 1, or 2. Preferably, z is selected from integers 0-6; morepreferably, is selected from integers 0-4; furthermore preferably, isselected from 0, 1, or 2.

Preferably, m is selected from 1 or 2. Preferably, n is selected from 1or 2. Preferably, k is selected from 1 or 2.

Preferably, at least two of R₁, R₂, and R₃ are same groups.

Preferably, at least two of R₁, R₂, and R₃ are hydrogen atoms.

Preferably, R₁, R₂, and R₃ are all hydrogen atoms; or two of R₁, R₂, andR₃ are hydrogen atoms, and the remaining one is selected from a fluorineatom, a chlorine atom, a bromine atom, a substituted or unsubstitutedC₁-C₆ linear or branched alkyl group, or a substituted or unsubstitutedC₁-C₆ alkoxy group. The substituent group is selected from one or moreof halogen atoms. Preferably, the substituent group is selected from afluorine atom.

Preferably, the compound represented by the Formula I-3 may bespecifically selected from one or more of the following compounds, butthis application is not limited thereto:

In the lithium-ion battery of the present application, in the compoundsrepresented by the Formula II-1 and the Formula II-2:

The C₀-C₁₂ alkylene group may be a straight chain alkylene group or abranched chain alkylene group. A preferable lower limit of a quantity ofcarbon atoms in the C₀-C₁₂ alkylene group is 1, 2, 3, 4, and 5, apreferable upper limit is 3, 4, 5, 6, 7, 8, 9, 10, 11, 12. Preferably, aC₀-C₁₀ alkylene group is selected; more preferably, a C₁-C₆ alkylenegroup is selected; furthermore preferably, a C₂-C₄ alkylene group isselected. Examples of C₀-C₁₂ alkylene group may specifically includemethylene, ethylene, propylene, isopropylidene, butylene, isobutylene,sec-butylene, pentylene, and hexylene.

The C₂-C₁₂ alkenylene group may be a straight chain alkenylene group ora branched chain alkenylene group, and a number of double bonds in theC₂-C₁₂ alkenylene group is preferably one. A preferable lower limit of aquantity of carbon atoms in the C₂-C₁₂ alkenylene group is 2, 3, 4, and5, and a preferable upper limit is 4, 5, 6, 7, 8, 9, 10, 11, and 12.Preferably, a C₂-C₁₀ alkenylene group is selected; more preferably, aC₂-C₆ alkenylene group is selected; furthermore preferably, a C₂-C₄alkenylene group is selected. Examples of C₂-C₁₂ alkenylene group mayspecifically include: vinylidene, allylene, isopropenylene, butylenegroup, and pentenylene.

The C₂-C₁₂ alkynylene group may be a straight-chain alkynylene group ora branched-chain alkynylene group, and a number of triple bonds in theC₂-C₁₂ alkynylene group is preferably 1. A preferable lower limit of aquantity of carbon atoms in the C₂-C₁₂ alkynylene group is 2, 3, 4, and5, and a preferable upper limit is 4, 5, 6, 7, 8, 9, 10, 11, and 12.Preferably, a C₂-C₁₀ alkynylene group is selected; more preferably, aC₂-C₆ alkynylene group is selected; still more preferably, a C₂-C₄alkynylene group is selected. Examples of the C₂-C₁₂ alkynylene groupmay specifically include: ethynylene, propynylene, isopropynylene, andpentynylene.

The halogen atom as the substituent group may be selected from one ormore of a fluorine atom, a chlorine atom, and a bromine atom, and ispreferably a fluorine atom.

(1) Specifically, the compound represented by the Formula II-1 is analiphatic dinitrile compound.

In the Formula II-1, preferably, R₅ is selected from a substituted orunsubstituted C₁-C₁₀ alkylene group, a substituted or unsubstitutedC₂-C₁₀ alkenylene group, a substituted or unsubstituted C₂-C₁₀alkynylene group; where the substituent group is selected from a halogenatom, preferably a fluorine atom. More preferably, R₅ is selected from aC₁-C₆ alkylene group, a C₂-C₆ alkenylene group, and a C₂-C₆ alkynylenegroup. Furthermore preferably, R₅ is selected from a C₂-C₄ alkylenegroup, a C₂-C₄ alkenylene group, and a C₂-C₄ alkynylene group.

Preferably, the compound represented by the Formula II-1 can be selectedfrom one or more of succinonitrile, glutaronitrile, adiponitrile,pimenonitrile, suberonitrile, azelaonitrile, sebaconitrile, undecanedinitrile, dodecane dinitrile, tetramethyl succinonitrile, methylglutaronitrile, butenedinitrile, 2-pentene dinitrile, hex-2-enedionitrile, hex-3-ene dinitrile, oct-4-ene dinitrile and oct-4-ynedinitrile.

More preferably, the compound represented by the Formula II-1 may beselected from one or more of succinonitrile, glutaronitrile,adiponitrile, butenedionitrile, 2-pentene dionitrile, and hexa-3-enedionitrile, and a specific structure is as follows:

(2) Specifically, the compound represented by the Formula II-2 is analiphatic polynitrile compound.

In the Formula II-2, preferably, R₆, R₇, and R₈ each are independentlyselected from a substituted or unsubstituted C₀-C₁₀ alkylene group, asubstituted or unsubstituted a C₂-C₁₀ alkenylene group, a substituted orunsubstituted C₂-C₁₀ alkynylene group; where the substituent group isselected from a halogen atom, preferably a fluorine atom. Morepreferably, R₆, R₇, and R₈ each are independently selected from a C₀-C₆alkylene group, a C₂-C₆ alkenylene group, and a C₂-C₆ alkynylene group.More preferably, R₆ is selected from a C₀-C₁ alkylene group, and R₇ andR₈ each are independently selected from a C₂-C₄ alkylene group, a C₂-C₄alkenylene group, and a C₂-C₄ alkynylene group.

Preferably, the compound represented by the Formula II-2 may be selectedfrom one or more of 1,2,3-propanetricarbonitrile,1,3,5-pentatricarbonitrile, and 1,3,6-hexanetricarbonitrile, and aspecific structure is as follows:

In the lithium-ion battery of the present application, the electrolytemay further contain an additive C. The additive C may be selected fromone or more of a cyclic carbonate compound containing a carbon-carbonunsaturated bond, a halogen-substituted cyclic carbonate compound, asulfate ester compound, a sultone compound, a disulfonate compound, asulfite compound, an aromatic compound, an isocyanate compound, aphosphazene compound, an acid anhydride compound, a phosphite compound,a phosphate compound, and a borate compound.

Preferably, the mass percentage of the additive C in the electrolyte is0.01%-30%.

(a) Cyclic Carbonate Compound Containing a Unsaturated Carbon-CarbonBond

The cyclic carbonate compound containing a carbon-carbon unsaturatedbond may be selected from one or more of the compounds represented byFormula III-0. In Formula III-0, R₂₀ is selected from a C₁-C₆ alkylenegroup substituted with an alkenyl group or an alkynyl group, asubstituted or unsubstituted C₂-C₆ linear alkenylene group, where thesubstituent group is selected from one or more of a halogen atom, aC₁-C₆ alkyl group, and a C₂-C₆ alkenyl group.

Preferably, the cyclic carbonate compound containing a carbon-carbonunsaturated bond may be specifically selected from one or more of thefollowing compounds, but the present application is not limited thereto:

(b) Halogen Substituted Cyclic Carbonate Compound

The halogen-substituted cyclic carbonate compound may be selected fromone or more of the compounds represented by Formula III-1. In theFormula III-1, R₂₁ is selected from a halogen-substituted C₁-C₆ alkylenegroup and a halogen-substituted C₂-C₆ alkenylene group.

Specifically, the halogen-substituted cyclic carbonate compound may beselected from or one or more of fluoroethylene carbonate (abbreviated asFEC), fluoropropylene carbonate (abbreviated as FPC), trifluoropropylenecarbonate (abbreviated as TFPC), trans-4,5-difluoro-1,3-dioxolane-2-oneor cis-4,5-difluoro-1,3-dioxolane-2-one (hereinafter the two arecollectively referred to as “DFEC”).

(c) Sulfate Compound

The sulfate compound is preferably a cyclic sulfate compound, and thecyclic sulfate compound may be selected from one or more of thecompounds represented by Formula III-2. In the Formula III-2, R₂₂ isselected from a substituted or unsubstituted C₁-C₆ alkylene group, asubstituted or unsubstituted C₂-C₆ alkenylene group, where thesubstituent group is selected from one or more of a halogen atom, aC₁-C₃ alkyl group, or a C₂-C₄ alkenyl group.

In the Formula III-2, preferably, R₂₂ is selected from a substituted orunsubstituted C₁-C₄ alkylene group, a substituted or unsubstituted C₂-C₄alkenylene group, where the substituent group is selected from one ormore of a halogen atom, a C₁-C₃ alkane, and a C₂-C₄ alkenyl group.

Preferably, the sulfate compound may be specifically selected from oneor more of the following compounds, but the present application is notlimited to this:

More preferably, the sulfate compound is selected from one or more ofethylene sulfate (abbreviated as DTD), trimethylene sulfite (abbreviatedas TMS), and propylene sulfate (abbreviated as PLS), the specificstructures thereof are as follows:

(d) Sultone Compound

The sultone compound may be selected from one or more of the compoundsrepresented by Formula III-3. In Formula III-3, R₂₃ is selected from asubstituted or unsubstituted C₁-C₆ alkylene group, a substituted orunsubstituted C₂-C₆ alkenylene group, where the substituent is selectedfrom one or more of a halogen atom, a C₁-C₃ alkyl group, and a C₂-C₄alkenyl group.

In Formula III-3, preferably, R₂₃ is selected from a substituted orunsubstituted C₁-C₄ alkylene group, a substituted or unsubstituted C₂-C₄alkenylene group, where the substituent group is selected from one ormore of a halogen atom, a C₁-C₃ alkane group and a C₂-C₄ alkenyl group.

Preferably, the sultone compound may be specifically selected from oneor more of the following compounds, but the present application is notlimited thereto:

More preferably, the sultone compound may be selected from one or moreof 1,3-propane sultone (abbreviated as PS) and 1,3-propene sultone(abbreviated as PES), and the specific structures are as follows:

(e) Disulfonate Compound

The disulfonate compound is a compound containing two sulfonic acidgroups (—S(═O)2O—), preferably selected from a methylene disulfonatecompound, and the methylene disulfonate compound may be selected fromone or more of the compounds represented by Formula III-4. In FormulaIII-4, R₂₄, R₂₅, R₂₆, and R₂₇ each are independently selected from ahydrogen atom, a halogen atom, a substituted or unsubstituted C₁-C₁₀alkyl group, a substituted or unsubstituted C₂-C₁₀ alkenyl group, wherethe substituent group is selected from one or more of a halogen atom, aC₁-C₃ alkyl group, and a C₂-C₄ alkenyl group.

In Formula III-4, preferably, R₂₄, R₂₅, R₂₆, and R₂₇ each areindependently selected from a hydrogen atom, a halogen atom, asubstituted or unsubstituted C₁-C₄ alkyl group, and a substituted orunsubstituted C₂-C₆ alkenyl group, where the substituent group isselected from one or more of a halogen atoms, a C₁-C₃ alkyl group, and aC₂-C₄ alkenyl group.

Preferably, the disulfonate compound may be specifically selected fromone or more of the following compounds, but the present application isnot limited to this:

More preferably, the disulfonate compound may be selected from methylenemethanedisulfonate (abbreviated as MMDS), and the specific structure isas follows:

(f) Sulfite Compound

The sulfite compound is preferably a cyclic sulfite compound, which canbe specifically selected from one or more of the compounds representedby Formula III-5. In Formula III-5, R₂₈ is selected from a substitutedor unsubstituted C₁-C₆ alkylene group, a substituted and a unsubstitutedC₂-C₆ alkenylene group, where the substituent group is selected from oneor more of a halogen atom, a C₁-C₃ alkyl group, a C₂-C₄ alkenyl group.

In Formula III-5, preferably, R₂₈ is selected from a substituted orunsubstituted C₁-C₄ alkylene group, a substituted or unsubstituted C₂-C₄alkenylene group, where the substituent group is selected from one ormore of a halogen atom, a C₁-C₃ alkane, and a C₂-C₄ alkenyl group.

Preferably, the sulfite compound may be selected from one or more ofethylene sulfite (abbreviated as ES), propylene sulfite (abbreviated asPS), and butylene sulfite (abbreviated as BS).

(g) Aromatic Compound

The aromatic compound may be selected from one or more ofcyclohexylbenzene, fluorocyclohexylbenzene compounds(1-fluoro-2-cyclohexylbenzene, 1-fluoro-3-cyclohexylbenzene,1-fluoro-4-cyclohexylbenzene), tert-butylbenzene, tert-amylbenzene,1-fluoro-4-tert-butylbenzene, biphenyl, terphenyl (ortho, meta, para),diphenyl ether, fluorobenzene, difluorobenzene (ortho, meta, para),anisole, 2,4-difluoroanisole, partially hydrogenated product ofterphenyl (1,2-dicyclohexylbenzene, 2-phenylbicyclohexyl,1,2-diphenylcyclohexane, o-cyclohexylbiphenyl).

Preferably, the aromatic compound may be selected from one or more ofbiphenyl, terphenyl (ortho, meta, para), fluorobenzene,cyclohexylbenzene, tert-butylbenzene, and tert-amylbenzene. Furtherpreferably, the aromatic compound may be selected from one or more ofbiphenyl, o-terphenyl, fluorobenzene, cyclohexylbenzene, andtert-amylbenzene.

(h) Isocyanate Compound

The isocyanate compound may be selected from one or more of methylisocyanate, ethyl isocyanate, butyl isocyanate, phenyl isocyanate,tetramethylene diisocyanate, hexamethylene diisocyanate, octamethylenediisocyanate, 1,4-phenylene diisocyanate, 2-isocyanatoethyl acrylate,and 2-isocyanatoethyl methacrylate.

Preferably, the isocyanate compound may be selected from one or more ofhexamethylene diisocyanate, octamethylene diisocyanate,2-isocyanatoethyl acrylate, and 2-isocyanatoethyl methacrylate.

(i) Phosphononitrile Compound

The phosphazene compound is preferably a cyclic phosphazene compound.The cyclic phosphazene compound may be selected from one or more ofmethoxy pentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, phenoxy pentafluorocyclotriphosphazene,and ethoxy heptafluorocyclotetraphosphazene.

Preferably, the cyclic phosphazene compound may be selected from one ormore of methoxy pentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, and phenoxypentafluorocyclotriphosphazene.

More preferably, the cyclic phosphazene compound can be selected frommethoxy pentafluorocyclotriphosphazene or ethoxypentafluorocyclotriphosphazene.

(j) Acid Anhydride Compound

The acid anhydride compound may be a chain acid anhydride or a cyclicacid anhydride. Specifically, the acid anhydride compound may beselected from one or more of acetic anhydride, propionic anhydride,succinic anhydride, maleic anhydride, 2-allyl succinic anhydride,glutaric anhydride, itaconic anhydride, and 3-sulfo-propionic anhydride.

Preferably, the acid anhydride compound may be selected from one or moreof succinic anhydride, maleic anhydride, and 2-allyl succinic anhydride.More preferably, the acid anhydride compound may be selected from one orboth of succinic anhydride and 2-allyl succinic anhydride.

(k) Phosphite Compound

The phosphite compound may be selected from a silane phosphite compound,and specifically may be selected from one or more of the compoundsrepresented by Formula III-6. In the Formula III-6, R₃₁, R₃₂, R₃₃, R₃₄,R₃₅, R₃₆, R₃₇, R₃₈, and R₃₉ each are independently selected from ahalogen-substituted or unsubstituted C₁-C₆ alkyl group.

Preferably, the silane phosphite compound may be specifically selectedfrom one or more of the following compounds, but the present applicationis not limited thereto:

(l) Phosphate Compound

The phosphate compound may be selected from a silane phosphate compound,and specifically may be selected from one or more of the compoundsrepresented by Formula III-7. In the Formula III-7, R₄₁, R₄₂, R₄₃, R₄₄,R₄₅, R₄₆, R₄₇, R₄₈, and R₄₉ each are independently selected from ahalogen-substituted or unsubstituted C₁-C₆ alkyl group.

Preferably, the silane phosphate compound may be specifically selectedfrom one or more of the following compounds, but the present applicationis not limited thereto:

(m) Borate Compound

The borate compound may be selected from a silane borate compound, andspecifically may be selected from one or more of the compoundsrepresented by Formula III-8. In Formula III-8, R₅₁, R₅₂, R₅₃, R₅₄, R₅₅,R₅₆, R₅₇, R₅₈, and R₅₉ each are independently selected from ahalogen-substituted or unsubstituted C₁-C₆ alkyl group.

Preferably, the silane borate compound can be specifically selected fromone or more of the following compounds, but the present application isnot limited thereto:

In the lithium-ion battery of the present application, the electrolytefurther includes an organic solvent and an electrolyte salt.

The organic solvent used in the electrolyte of the example of thepresent application may include a cyclic carbonate and a chaincarbonate, which may further improve the cycle performance and storageperformance under high-temperature and high-voltage conditions, andwhich will adjust the conductivity of the electrolyte to an appropriaterange. Thus it is more favorable for each additive to achieve a betterfilm-forming effect.

The organic solvent used in the electrolyte of the example of thepresent application may further include a carboxylic acid ester, thatis, the organic solvent according to the present application may includea mixture of cyclic carbonate, chain carbonate, and carboxylic acidester. Carboxylic acid ester has the characteristics of large dielectricconstant and low viscosity, which can effectively prevent theassociation of ions with anions in the electrolyte, and are moreadvantageous to and cyclic carbonates and chain carbonates in terms ofion conduction, especially at low temperature, thus the electrolyte canbe guaranteed to good ion conductivity.

Based on the total mass of the organic solvent: the mass percentage ofthe cyclic carbonate may be 15% to 55%, preferably 25% to 50%; the masspercentage of the chain carbonate may be 15% to 74%, preferably 25% to70%; the mass percentage of the the carboxylic acid ester may be 0.1% to70%, preferably 5% to 50%.

Specifically, the cyclic carbonate may be selected from one or more ofethylene carbonate, propylene carbonate, 1,2-butene carbonate, and2,3-butylene glycol carbonate. More preferably, the cyclic carbonate maybe selected from one or more of ethylene carbonate and propylenecarbonate.

Specifically, the chain carbonate may be an asymmetric chain carbonateselected from one or more of ethyl methyl carbonate, methyl propylcarbonate, methyl isopropyl carbonate, methyl butyl carbonate, andethylene propyl carbonate; the chain carbonate may also be a symmetricchain carbonate selected from one or more of dimethyl carbonate, diethylcarbonate, dipropyl carbonate, dibutyl carbonate; the chain carbonatemay also be a mixture of the abovementioned asymmetric chain carbonateand symmetric chain carbonate.

Specifically, the carboxylic acid ester may be selected from one or moreof methyl pivalate, ethyl pivalate, propyl pivalate, butyl pivalate,methyl butyrate, ethyl butyrate, propyl butyrate, butyrate butyl ester,methyl propionate, ethyl propionate, propyl propionate, butylpropionate, methyl acetate, ethyl acetate, propyl acetate, and butylacetate.

As the electrolyte salt used in the present application, the followinglithium salts can be suitably exemplified.

[Li Salt-Type 1]: “a complex salt of Lewis acid with LiF” selected fromone or more LiPF₆, LiBF₄, LiAsF₆, LiSbF₆, LiPF₄(CF₃)₂, LiPF₃(C₂F₅)₃,LiPF₃(CF₃)₃, LiPF₃(iso-C₃F₇)₃ and LiPF₅(iso-C₃F₇), where preferablyselected from LiPF₆, LiBF₄, LiAsF₆, and more preferably selected fromLiPF₆, LiBF₄, may be suitably exemplified.

[Li Salt-Type 2]: “an imine or methylated lithium salt” selected fromone or more of (CF₂)₂(SO₂)₂NLi (cyclic), (CF₂)₃(SO₂)₂NLi (cyclic) andLiC(SO₂CF₃)₃ may be suitably exemplified.

[Li Salt-Type 3]: “a lithium salt containing a S(═O)₂O structure”selected from one or more of LiSO₃F, LiCF₃SO₃, CH₃SO₄Li, C₂H₅SO₄Li,C₃H₇SO₄Li, lithium trifluoro((methylsulfonyl)oxy) borate (LiTFMSB),lithium pentafluoro((methylsulfonyl)oxy)phosphate (LiPFMSP), where morepreferably selected from LiSO₃F, CH₃SO₄Li, C₂H₅SO₄Li or LiTFMSB, may besuitably exemplified.

[Li Salt-Type 4]: “a lithium salt containing a P═O or Cl═O structure”selected from one or more of LiPO₂F₂, Li₂PO₃F, and LiClO₄, wherepreferably selected from LiPO₂F₂, Li₂PO₃F, may be suitably exemplified.

[Li salt-type 5]: “a lithium salt with oxalate ligand as a positive ion”selected from one or more of lithium bis[oxalate-O,O′] borate (LiBOB),lithium difluoro[oxalate-O,O′] borate, lithium difluorobis[oxalate-O,O′]phosphate (LiPFO) and lithium tetrafluoro[oxalate-O,O′] phosphate, wheremore preferably selected from LiBOB and LiPFO, may be suitablyexemplified.

The abovementioned lithium salts can be used individually or incombination. Preferably, the lithium salt is selected from one or moreof LiPF₆, LiP₂F₂, Li₂PO₃F, LiBF₄, LiSO₃F, lithiumtrifluoro((methylsulfonyl)oxy) borate (LiTFMSB), lithiumbis[oxalate-O,O′] borate (LiBOB), lithium difluorobis[oxalate-O,O′]phosphate (LiPFO) and lithium tetrafluoro[oxalate-O,O′] phosphate. Morepreferably, the lithium salt is selected from one or more of LiPF₆,LiBF₄, LiSO₃F, lithium trifluoro((methylsulfonyl)oxy) borate (LiTFMSB),LiPO₂F₂, lithium bis[oxalate-O,O′] borate (LiBOB) and lithiumdifluorobis[oxalate-O,O′] phosphate (LiPFO). More preferably, thelithium salt is LiPF₆.

In the lithium-ion battery of the present application, the preparationmethod of the electrolyte is not limited, and can be prepared accordingto a conventional method for preparing an electrolyte.

In the lithium-ion battery of the present application, preferably, theconductivity of the electrolyte at 25° C. is 4 mS/cm to 12 mS/cm.

In the lithium-ion battery of the present application, preferably,Li_(x1)Co_(y1)M_(1-y1)O_(2-z1)Q_(z1) may be specifically selected fromone or more of LiCo_(0.9)Zr_(0.1)O₂, LiCo_(0.9)Ti_(0.1)O₂,Li_(1.05)Co_(0.8)Mg_(0.2)O₂,Li_(1.01)Co_(0.98)Mg_(0.01)Ti_(0.005)Al_(0.005)O₂,Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1),Li_(1.1)Co_(0.95)Mg_(0.01)Zr_(0.01)Al_(0.03)O₂,Li_(1.04)Co_(0.95)Mg_(0.02)Zr_(0.03)O_(1.95)F_(0.05),Li_(1.06)Co_(0.96)Mg_(0.02)Ti_(0.02)O₂,Li_(1.08)Co_(0.97)Mg_(0.01)Zr_(0.01)Al_(0.01)O_(1.9)S_(0.1),Li_(1.09)Co_(0.98)Mg_(0.01)Ti_(0.005)Al_(0.005)O₂,Li_(1.085)Co_(0.98)Zr_(0.01)Ti_(0.005)Al_(0.005)O_(1.9)Cl_(0.1),Li_(1.03)Co_(0.96)Mg_(0.01)Zr_(0.01)Ti_(0.01)Al_(0.01)O₂,Li_(1.04)Co_(0.97)Zr_(0.01)Al_(0.02)O_(1.9)F_(0.1),Li_(1.07)Co_(0.97)Zr_(0.01)Ti_(0.01)Al_(0.01)O_(1.9)S_(0.1),Li_(1.02)Co_(0.96)Mg_(0.02)Zr_(0.015)Ti_(0.005)O_(1.9)S_(0.1),Li_(1.03)Co_(0.98)Ti_(0.01)Al_(0.01)O_(1.9)Cl_(0.1),Li_(1.05)Co_(0.97)Mg_(0.01)Zr_(0.01)Al_(0.01)O_(1.9)Cl_(0.1),Li_(1.04)Co_(0.95)Zr_(0.02)Ti_(0.03)O_(1.9)F_(0.1),Li_(1.09)Co_(0.97)Mg_(0.02)Ti_(0.01)O_(1.95)F_(0.05),Li_(1.03)Co_(0.95)Mg_(0.03)Ti_(0.02)O_(1.9)S_(0.1),Li_(1.04)Co_(0.97)Zr_(0.01)Ti_(0.01)Al_(0.01)O_(1.9)S_(0.1).

In the lithium-ion battery of the present application, the positiveactive material may further include one or more of lithium nickel oxide,lithium manganese oxide, lithium nickel manganese oxide, lithium nickelcobalt manganese oxide, lithium nickel cobalt aluminum oxide, and acompound obtained by adding one or more of other transition metals ornon-transition metals to the aforementioned oxides.

In the lithium-ion battery of the present application, the positiveelectrode sheet further includes a binder and a conductive agent, and apositive slurry containing the positive active material, the binder andthe conductive agent is coated on a positive current collector, and thendried to obtain the positive electrode sheet. Type and content of theconductive agent and the binder are not specifically limited, and may beselected according to actual needs. The type of the positive currentcollector is also not specifically limited, and can be selectedaccording to actual needs, and is preferably an aluminum foil.

In the lithium-ion battery of the present application, the negativeactive material in the negative electrode sheet includes one or more ofsoft carbon, hard carbon, artificial graphite, natural graphite, Si,SiO₂, Si/C composite material, Si alloy, lithium titanate, and metalcapable of forming an alloy with lithium, wherein 0<x2≤2.

In the lithium-ion battery of the present application, the negativeelectrode sheet further includes a binder and a conductive agent, and anegative slurry containing the negative active material, the binder andthe conductive agent is coated on the negative current collector, andthen dried to obtain the negative electrode sheet. Type and content ofthe conductive agent and the binder are not specifically limited, andmay be selected according to actual needs. Type of the negative currentcollector is also not specifically limited, and can be selectedaccording to actual needs, and is preferably a copper foil.

In the lithium-ion battery of the present application, the separationfilm is disposed between the positive electrode sheet and the negativeelectrode sheet to play a role of isolation. The specific type of theseparation film is specifically limited, and may be any material of aseparation film used in existing lithium-ion batteries, such aspolyethylene, polypropylene, polyvinylidene fluoride and theirmultilayer composite film, but not limited to these.

In the lithium-ion battery of the present application, a charge cut-offvoltage of the lithium-ion battery is not less than 4.2V, that is, thelithium-ion battery may be used in a high voltage state of not less than4.2V. Preferably, the charge cut-off voltage of the lithium-ion batteryis not less than 4.35V.

The lithium-ion battery of the present application may be either ahard-shell lithium-ion battery or a soft-packaged lithium-ion battery.The hard shell lithium-ion battery preferably uses a hard shell ofmetal. The soft-packaged lithium-ion battery preferably uses a packagingbag as a battery housing, the packaging bag usually includes anaccommodating part and a sealing part, where the accommodating part isused to accommodate the electrode assembly and the electrolyte, and thesealing part is used to seal the electrode assembly and the electrolyte.The electrolyte of the present application improves the performance ofsoft-packaged lithium-ion batteries more obviously, becausesoft-packaged lithium-ion batteries are prone to swelling during use,and the electrolyte of the present application may greatly reduce thegas production of the battery, and avoid shortening life caused by theswelling of the soft-packaged lithium-ion batteries.

In the lithium-ion battery of the present application, the additive Amay be synthesized by the following method.

(1) Preparation of the Compound Represented by the Formula I-1

A reaction scheme is as follows:

A specific preparation process includes:

adding aqueous solution P-2 with a concentration of 30%-40% dropwise toa raw material P-1 within 20 min 60 min with quickly stirring thesolution. After the dropwise addition is completed, quickly stirring thesolution for 15 h-30 h. Stirring the solution in an oil bath at 70°C.-90° C. under reflux for 3 h-5 h to obtain a colorless, fuming andviscous liquid intermediate product I-1-1. Then adding K₂CO₃, KI, andanhydrous acetonitrile, and quickly stirring them to form a solid-liquidmixture. Quickly adding a raw material P-3 at 40° C.-60° C., thenstirring them for 10 h-20 h, and cooling the mixture to roomtemperature. Then performing separation and purification to obtain thecompound represented by the Formula I-1.

(2) Preparation of the Compound Represented by the Formula I-2

A reaction scheme is as follows:

A specific preparation process includes:

mixing anhydrous sodium carbonate, a raw material P-4 and a raw materialP-3 in absolute ethanol, and stirring for 2 h-5 h for a reaction;repeatedly washing with hot ethanol for a plurality of times to obtain acrude product, and performing recrystallization to obtain the compoundrepresented by the Formula I-2.

(3) Preparation of the Compound Represented by the Formula I-3

A reaction scheme is as follows:

A specific preparation process includes:

mixing anhydrous sodium carbonate, a raw material P-5 and a raw materialP-3 in anhydrous ethanol, and stirring for 2 h-5 h for a reaction;repeatedly washing with hot ethanol for a plurality of times to obtain acrude product, and performing recrystallization to obtain the compoundrepresented by the Formula I-3.

In some examples, the lithium-ion battery may include an outer packagefor encapsulating the positive electrode sheet, the negative electrodesheet, and the electrolyzable substance. As an example, the positiveelectrode sheet, the negative electrode sheet and the separation filmmay be laminated or wound to form an electrode assembly of a laminatedstructure or an electrode assembly of a wound structure, the electrodeassembly is encapsulated in an outer package; the electrolyzablesubstance may be an electrolyte, which infiltrates in the electrodeassembly. There may be one or more electrode assemblies in thelithium-ion battery, depending on needs.

In some examples, the outer package of the lithium-ion battery may be asoft package, for example, a soft bag. A material of the soft packagemay be plastic, for example, may include one or more of polypropylenePP, polybutylene terephthalate PBT, polybutylene succinate PBS, and thelike. Alternatively, the outer package of the lithium-ion battery may bea hard shell, for example, an aluminum shell.

Shape of the lithium-ion battery in the present application is notparticularly limited, and may be of a cylindrical, square, or any othershape. FIG. 4 shows an example of a lithium-ion battery 5 of a squarestructure.

In some Examples, lithium-ion batteries may be assembled into a batterymodule, and the battery module may include a plurality of lithium-ionbatteries, and a specific quantity may be adjusted according toapplication and capacity of the battery module.

FIG. 5 shows as an example of a battery module 4. Referring to FIG. 5,in the battery module 4, a plurality of lithium-ion batteries 5 may besequentially arranged along a length direction of the battery module 4;or certainly, may be arranged in any other manner. Furthermore, theplurality of lithium-ion batteries 5 may be fixed by using fasteners.

Optionally, the battery module 4 may further include a housing with anaccommodating space, and the plurality of lithium-ion batteries 5 areaccommodated in the accommodating space.

In some Examples, the above-mentioned battery modules can also beassembled into a battery pack, and the quantity of battery modulesincluded in the battery pack can be adjusted according to applicationand capacity of the battery pack.

FIG. 6 and FIG. 7 show an example of a battery pack 1. Referring to FIG.6 and FIG. 7, the battery pack 1 may include a battery cabinet and aplurality of battery modules 4 disposed in the battery cabinet. Thebattery cabinet includes an upper cabinet body 2 and a lower cabinetbody 3. The upper cabinet body 2 can cover the lower cabinet body 3 andform an enclosed space for accommodating the battery module 4. Theplurality of battery modules 4 may be arranged in the battery cabinet inany manner.

An apparatus according to a second aspect of the present applicationwill be described next.

In a second aspect of the present application, an apparatus is provided.The apparatus includes the lithium-ion battery in the first aspect ofthe present application, and the lithium-ion battery supplies power tothe apparatus. The apparatus may be, but is not limited to, a mobiledevice (for example, a mobile phone or a notebook computer), an electricvehicle (for example, a full electric vehicle, a hybrid electricvehicle, a plug-in hybrid electric vehicle, an electric bicycle, anelectric scooter, an electric golf vehicle, or an electric truck), anelectric train, a ship and a satellite, an energy storage systems, andthe like.

A lithium-ion battery, a battery module, or a battery pack may beselected for the apparatus according to requirements for using theapparatus.

FIG. 8 shows an example of apparatus. The apparatus is a full electricvehicle, a hybrid electric vehicle, or a plug-in hybrid electricvehicle, or the like. In order to meet a requirement of the apparatusfor high power and high energy density of a lithium-ion battery, abattery pack or a battery module may be used.

As another example, the apparatus may be a mobile phone, a tabletcomputer, a notebook computer, or the like. The apparatus is generallyrequired to be light and thin, and may use a lithium-ion battery as itspower source.

To make the purpose, technical solutions, and beneficial technicaleffects of the present application clearer, the present application willbe further described below in detail with reference to Examples. Itshould be understood that the Examples described in this specificationare merely intended to explain the present application, but not to limitthe present application. Formulations, proportions, and the like of theexamples may be adjusted according to local conditions withoutsubstantial effect on results.

All reagents, materials, and instruments that are used in Examples andComparative Examples are commercially available unless otherwisespecified. Specific synthesis processes of additives A1, A2, and A3 areas follows, and other types of additives A may be synthesized accordingto similar methods.

Synthesis of the Additive A1:

37% formaldehyde aqueous solution is added dropwise to1,3-propanediamine within 0.5 h with quick stirring. After the dropwiseaddition is completed, the solution was still quickly stirred for 20 h.Then the solution was stirred in an oil bath at 80° C. reflux for 4 h toobtain intermediate product hexahydropyrimidine as a colorless, fuming,and viscous liquid. K₂CO₃, KI, and anhydrous acetonitrile were added,followed by quick stirring to form a solid-liquid mixture. ThenP-chloropropionitrile was added at 60° C. within 0.5 h. The mixture wasstirred for 17 h, and cooled to room temperature. Then the mixture wassubjected to separation and purification to obtain A1. Carbon nuclearmagnetic resonance spectrum was shown in FIG. 1.

Synthesis of the Additive A2:

Anhydrous sodium carbonate, piperazine and O-chloropropionitrile aremixed in absolute ethanol, and stirred for 4 hours for reaction. Themixture was repeatedly washed with hot ethanol for a plurality of timesto obtain a crude product, and subjected to recrystallization to obtainA2. Carbon nuclear magnetic resonance spectrum was shown in FIG. 2.

Synthesis of the Additive A3:

Anhydrous sodium carbonate, 1,3,5-s-triazine and chloroacetonitrile weremixed in absolute ethanol, and stirred for 4 h for reaction. The mixturewas repeatedly washed with hot ethanol for a plurality of times toobtain a crude product, and subjected to recrystallization to obtain A3.Carbon nuclear magnetic resonance spectrum is shown in FIG. 3.

In Examples 1-24 and Comparative Example 1-2, lithium-ion batteries wereprepared according to the following method.

(1) Preparation of an Electrolyte

A mixed solution of ethylene carbonate (EC for short), ethyl methylcarbonate (EMC for short) and diethyl carbonate (DEC for short) was usedas an organic solvent, where a mass ratio of EC, EMC and DEC was 1:1:1.LiPF₆, was used as a lithium salt in an amount of 12.5% relative to thetotal mass of the electrolyte. Additives were added according toelectrolyte composition as shown in Table 1, where the content of eachadditive component was calculated relative to the total mass of theelectrolyte.

The additives A and B used in the Examples and Comparative Examples areabbreviated as follows:

(2) Preparation of a Positive Electrode Sheet

A positive active material, a binder PVDF, and a conductive agentacetylene black shown in Table 1 were mixed at a mass ratio of 98:1:1.N-methylpyrrolidone was added. The resulting mixture was stirred byusing a vacuum mixer until the mixture was stable and uniform, to obtaina positive slurry. The positive slurry was uniformly coated onto analuminum foil. The aluminum foil was dried at room temperature, andtransferred to a blast oven at 120° C. to dry for 1 h. Then the aluminumfoil was cold-pressed and cut to obtain a positive electrode sheet.

(3) Preparation of a Negative Electrode Sheet

A negative active material graphite, a conductive agent acetylene black,a thickening sodium carboxymethyl cellulose solution, and a binderstyrene-butadiene rubber emulsion were mixed at a mass ratio of97:1:1:1. Deionized water was added. The resulting mixture was stirredby using a vacuum mixer until the mixture was stable and uniform, toobtain a negative slurry. The negative slurry was uniformly coated ontoa copper foil. The copper foil was dried at room temperature, andtransferred to a blast oven at 120° C. for 1 h. Then the copper foil wascold-pressed and cut to obtain a negative electrode sheet.

(4) Preparation of a Lithium-Ion Battery

The positive electrode sheet, the negative electrode sheet and aPP/PE/PP separation film were wound to obtain the electrode assembly,the electrode assembly was placed into an aluminum plastic film of apackaging bag, followed by injection of the electrolyte, and then aprocedure including sealing, standing, hot-pressing and cold-pressing,forming, gas exhausting, and capacity testing were performed to obtain alithium-ion battery.

TABLE 1 Parameters of Examples 1-24 and Comparative Examples 1-2Additive A Additive B Additive C Positive active material Type AmountType Amount Type Amount Example 1Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A1 0.1% B12.0% / / Example 2Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A1 1.0% B12.0% / / Example 3Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A1 2.0% B12.0% / / Example 4Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A1 3.5% B12.0% / / Example 5Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A1 6.0% B12.0% / / Example 6Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A1 8.0% B12.0% / / Example 7Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A1 10.0%B1 2.0% / / Example 8Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A2 2.0% B60.1% / / Example 9Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A2 2.0% B60.5% / / Example 10Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A2 2.0% B61.0% / / Example 11Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A2 2.0% B63.0% / / Example 12Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A2 2.0% B65.0% / / Example 13Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A2 2.0% B68.0% / / Example 14Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A2 2.0% B6 10% / / Example 15Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A1 2.0% B12.0% EEC 2.0% Example 16Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A1 2.0% B12.0% DTD 2.0% Example 17 Li_(1.1)Co_(0.95)Mg_(0.01)Zr_(0.01)Al_(0.03)O₂A3 2.0% B2 2.0% / / Example 18Li_(1.04)Co_(0.95)Mg_(0.02)Zr_(0.03)O_(1.95)F_(0.05) A4 2.0% B2 2.0% / /Example 19 Li_(1.08)Co_(0.97)Mg_(0.01)Zr_(0.01)Al_(0.01)O_(1.9)S_(0.1)A5 2.0% B3 2.0% / / Example 20Li_(1.085)Co_(0.98)Zr_(0.01)Ti_(0.005)Al_(0.005)O_(1.9)Cl_(0.1) A6 2.0%B3 2.0% / / Example 21Li_(1.03)Co_(0.96)Mg_(0.01)Zr_(0.01)Ti_(0.01)Al_(0.01)O₂ A7 2.0% B4 2.0%/ / Example 22 Li_(1.06)Co_(0.96)Mg_(0.02)Ti_(0.02)O₂ A8 2.0% B4 2.0% // Example 23 Li_(1.09)Co_(0.98)Mg_(0.01)Ti_(0.005)O₂ A9 2.0% B5 2.0% / /Example 24 Li_(1.04)Co_(0.97)Zr_(0.01)Al_(0.02)O_(1.9)F_(0.1) A10  2.0%B5 2.0% / / Comparative LiCoO₂ / / / / / / Example 1 Comparative LiCoO₂/ / B1 2.0% / / Example 2

Tests for lithium-ion batteries are described below.

(1) Cyclic Performance Test for a Lithium-Ion Battery at NormalTemperature and High Voltage

At 25° C., the lithium-ion battery is charged at a constant current of 1C until a voltage of 4.35 V is reached, further charged at a constantvoltage of 4.35 V until a current of 0.05 C is reached, and thendischarged at a constant current of 1 C until a voltage of 3.0 V isreached. This is a charge/discharge cycle process, and the obtaineddischarge capacity at this time is the discharge capacity at the firstcycle. A lithium-ion battery is subjected to charge/discharge testaccording to the foregoing method for 200 cycles, to determine adischarge capacity at the 200^(th) cycle.

Capacity retention rate (%) of the lithium-ion battery after 200cycles=(the discharge capacity of the lithium-ion battery after 200cycles/the discharge capacity of the lithium-ion battery at the firstcycle)×100%.

(2) Cyclic Performance Test for a Lithium-Ion Battery UnderHigh-Temperature and High-Voltage Conditions

At 45° C., the lithium-ion battery is charged at a constant current of 1C until a voltage of 4.35 V is reached, further charged at a constantvoltage of 4.35 V until a current of 0.05 C is reached, and thendischarged at a constant current of 1 C until a voltage of 3.0 V isreached. This is a charge/discharge cycle process, and the obtaineddischarge capacity at this time is the discharge capacity at the firstcycle. A lithium-ion battery is subjected to charge/discharge testaccording to the foregoing method for 200 cycles, to determine adischarge capacity at the 200^(th) cycle.

Capacity retention rate (%) of a lithium-ion battery after 200cycles=(the discharge capacity of the lithium-ion battery after 200cycles/the discharge capacity of the lithium-ion battery at the firstcycle)×100%.

(3) Storage Performance Test for a Lithium-Ion Battery at a HighTemperature

At 25° C. the lithium-ion battery is charged at a constant current of0.5 C until a voltage of 4.35 V is reached, and then charged at aconstant voltage of 4.35 V until a current of 0.05 C is reached. Thethickness of the lithium-ion battery is tested and denoted the thicknessas h₀. Then the lithium-ion battery is placed in a constant-temperaturebox at 85° C., stored for 24 h, and then taken out. Then the thicknessof the lithium-ion battery is tested again and denoted as h₁.

Thickness expansion rate (%) of the lithium-ion battery after storage at85° C. for 24 h=[(h₁−h₀)/h₀]×100%.

TABLE 2 Performance test results of Examples 1-24 and ComparativeExamples 1-2 Capacity retention Capacity retention Thickness rate after200 rate after 200 expansion cycles at 25° cycles at 45° rate at 85°C./4.35 V C./4.35 V C./24 h Example 1 91% 88% 15%  Example 2 94% 90% 9%Example 3 98% 94% 4% Example 4 96% 92% 3% Example 5 93% 87% 2% Example 688% 80% 2% Example 7 82% 74% 1% Example 8 96% 91% 8% Example 9 98% 93%6% Example 10 98% 94% 5% Example 11 96% 92% 4% Example 12 92% 88% 2%Example 13 84% 77% 1% Example 14 78% 69% 1% Example 15 99% 96% 4%Example 16 98% 95% 2% Example 17 97% 93% 5% Example 18 96% 92% 4%Example 19 98% 94% 6% Example 20 95% 91% 3% Example 21 96% 92% 5%Example 22 98% 94% 3% Example 23 97% 93% 4% Example 24 96% 92% 4%Comparative 85% 78% 42%  Example 1 Comparative 89% 85% 18%  Example 2

It can be seen from comparisons between Examples 1-24 and ComparativeExamples 1-2 that lithium-ion batteries of the present application havesuper cycle performance and storage performance under high-temperatureand high-voltage conditions.

Compared with Comparative Example 1, in Examples of the presentapplication, the metal ion M-doped lithium cobalt oxide materialLi_(x1)Co_(y1)M_(1-y1)O_(2-z1)Q_(z1) was used as the positive activematerial, and the combined additive of additive A and additive B wasused as an electrolyte additive. The doping element M served as aframework in the positive active material, which can reduce latticedeformation during deep delithiation process of the positive activematerial, delay degradation of bulk structure of the positive activematerial, and greatly improve structural stability of the lithium-ionbattery when the lithium-ion battery was used under high-voltageconditions. The additive A was a polynitrile six-memberednitrogen-heterocyclic compound with a relatively low oxidationpotential, such that a stable complex layer was formed on a surface ofthe positive active material during formation of the battery, whicheffectively passivated the surface of the positive active material,reduced surface activity of the positive active material, and avoideddirect contact between the electrolyte and the surface of the positiveactive material, thereby greatly reducing surface side reactions, andcorrespondingly reducing lithium ions consumed in the side reactions,and thus greatly decreasing a consumption rate of reversible lithiumions. The actual effect finally manifested was that capacity retentionrate of the lithium-ion battery after cycling was greatly increased. Dueto the production gas in some surface side reactions, the reduction ofsurface side reactions further indicated a decrease in gas production ofthe battery. The actual effect finally manifested was that thicknessexpansion of the lithium-ion battery was significantly reduced at hightemperature. The additive B was an aliphatic dinitrile or polynitrilecompound with a higher oxidation potential, which can stably exist inthe electrolyte for a long time and can repair the damaged complex layer(formed by the additive A) at any time during cycling or hightemperature storage, reduce the dissolution of transition metal ions,and greatly reduce the damage of the transition metal to the SEI filmdeposited on the negative electrode after the dissolution of thetransition metal. Therefore, the present application can significantlyimprove the cycle performance and storage performance of lithium-ionbatteries under high-temperature and high-voltage conditions.

Compared with the linear nitrile compound used in Comparative Example 2,the polynitrile six-membered nitrogen-heterocyclic compound of thepresent application has a special six-membered nitrogen-heterocyclicstructure with a spacing between nitrile groups closer to that betweentransition metals on the surface of the positive active material. Thiscan maximize complexation of the nitrile group and allow more nitrilegroups to have a complexation effect. Therefore, the polynitrilesix-membered nitrogen-heterocyclic compound of the present applicationhad stronger coverage on a transition metal on the surface of thepositive active material, better passivation effect on the surface ofthe positive active material, and also outstanding improvement on cycleperformance and storage performance of the lithium-ion battery.

It can be further seen from Examples 1-7 that, when an end-of-chargevoltage was fixed at 4.35 V, with an increase (from 0.1% to 10%) in theamount of the additive A, the capacity retention rate of the lithium-ionbattery after cycling at 25° C. and 45° C. showed an ascent and thenshowed a decline trend, and the thickness expansion rate after storageat 85° C. for 24 h was decreasing. This was because when the amount ofthe additive A was relatively large, the complex layer formed by theadditive A being adsorbed on the surface of the positive active materialwas likely to be thicker and denser, affecting diffusion and migrationof lithium ions, and greatly increasing positive electrode impedance.Secondly, the additive A consumed lithium ions while forming the complexlayer, reducing lithium ions available for cycling. Finally, arelatively large amount of the additive A caused an increase in overallviscosity of the electrolyte and a decrease in an ionic conductivity, sothat the capacity retention rate of the lithium-ion battery aftercycling at 25° C. and 45° C. showed an ascent and then showed a declinetrend. Therefore, the amount of the additive A needs to be appropriate.Preferably, the amount is 0.1%-10%; more preferably, is 0.1%-6%; furthermore preferably, is 0.1%-3.5%.

It can be seen from Examples 8-14 that when an end-of-charge voltage wasfixed at 4.35 V, with an increase (from 0.1% to 10%) in the amount ofthe additive B, the capacity retention rate of the lithium-ion batteryafter cycling at 25° C. and 45° C. showed an ascent and then showed adecline trend, and the thickness expansion rate after storage at 85° C.for 24 h was decreasing. This was because when the additive B was addedin a large amount, it has a stronger repairing effect on the complexlayer on the surface of the positive active material, and the complexlayer formed on the surface of the positive active material is likely tobe thicker and denser, the positive and negative electrode impedancesincrease significantly, so that the capacity retention rate of thelithium-ion battery after cycling at 25° C. and 45° C. showed an ascentand then showed a decline trend. Therefore, the amount of the additive Balso needs to be appropriate. Preferably, the amount is 0.1%-10.0%; morepreferably, is 0.1%-5.0%.

According to the disclosure and guidance in this specification, a personskilled in the art to which this application relates may also makeappropriate changes and modifications to the foregoing embodiments.Therefore, this application is not limited to the specific embodimentsdisclosed and described above, and modifications and changes to thepresent application shall also fall within the protection scope of theclaims of this application. In addition, although some specific termsare used in this specification, these terms are merely intended for easeof description, and do not constitute any limitation on thisapplication.

What is claimed is:
 1. A lithium-ion battery, comprising an electrodeassembly and an electrolyte, the electrode assembly comprising apositive electrode sheet, a negative electrode sheet and a separationfilm; wherein a positive active material in the positive electrode sheetcomprises Li_(x1)Co_(y1)M_(1-y1)O_(2-z1)Q_(z1), 0.5≤x1≤1.2, 0.8≤y1<1.0,0≤z1≤0.1, M is selected from one or more of the group consisting of Al,Ti, Zr, Y, and Mg, and Q is selected from one or more of the groupconsisting of F, Cl, and S; the electrolyte also contains an additive Aand an additive B, the additive A is selected from one or more of thegroup consisting of compounds represented by Formula I-1, and Formula1-3, and the additive B is selected from one or more of the groupconsisting of compounds represented by Formula II-1 and Formula II-2;

in Formula I-1 and Formula I-3: R₁, R₂, R₃, and R₄ are eachindependently selected from the group consisting of a hydrogen atom, ahalogen atom, a substituted or unsubstituted C₁-C₁₂ alkyl group, asubstituted or unsubstituted C₁-C₁₂ alkoxy group, a substituted orunsubstituted C₁-C₁₂ amine group, a substituted or unsubstituted C₂-C₁₂alkenyl group, a substituted or unsubstituted C₂-C₁₂ alkynyl group, asubstituted or unsubstituted C₆-C₂₆ aryl group, and a substituted orunsubstituted C₂-C₁₂ heterocyclic group, wherein a substituent group isselected from one or more of the group consisting of a halogen atom, anitrile group, a C1-C6 alkyl group, a C₂-C₆ alkenyl group, and a C₁-C₆alkoxy group; x, y, z are each independently selected from integers of0-8; and m, n, k are each independently selected from integers of 0-2;

in Formula II-1 and Formula II-2: R₅ is selected from the groupconsisting of a substituted or unsubstituted C₁-C₁₂ alkylene group, asubstituted or unsubstituted C₂-C₁₂ alkenylene group, and a substitutedor unsubstituted C₂-C₁₂ alkynylene group, and R₆, R₇, and R₈ are eachindependently selected from the group consisting of substituted orunsubstituted C₀-C₁₂ alkylene group, substituted or unsubstituted C₂-C₁₂alkenylene group, and substituted or unsubstituted C₂-C₁₂ alkynylenegroup, wherein a substituent group is selected from one or more of thegroup consisting of a halogen atom, a nitrile group, a C₁-C₆ alkylgroup, a C₂-C₆ alkenyl group, and a C₁-C₆ alkoxy group; a masspercentage of the additive A in the electrolyte is 0.1% to 3.5% and amass percentage of the additive B in the electrolyte is 0.1% to 5%. 2.The lithium-ion battery according to claim 1, wherein in Formula I-1 andFormula I-3: R₁, R₂, R₃, and R₄ are each independently selected from thegroup consisting of a hydrogen atom, a halogen atom, a substituted orunsubstituted C₁-C₃ linear or branched alkyl group, a substituted orunsubstituted C₅-C₇ cyclic alkyl group, a substituted or unsubstitutedC₁-C₃ alkoxy group, a substituted or unsubstituted C₁-C₃ amine group, asubstituted or unsubstituted C₂-C₃ alkenyl group, a substituted orunsubstituted C₂-C₃ alkynyl group, a substituted or unsubstituted C₆-C₈aryl group, and a substituted or unsubstituted C₂-C₇ heterocyclic group,wherein a substituent group is selected from halogen atoms; and/or, inFormula II-1 and Formula II-2: R₅ is selected from the group consistingof a substituted or unsubstituted C₁-C₁₀ alkylene group, a substitutedor unsubstituted C₂-C₁₀ alkenylene group, and a substituted orunsubstituted C₂-C₁₀ alkynylene group, and R₆, R₇, and R₈ are eachindependently selected from the group consisting of a substituted orunsubstituted C₀-C₁₀ alkylene group, a substituted or unsubstitutedC₂-C₁₀ alkenylene group, and a substituted or unsubstituted C₂-C₁₀alkynylene group, wherein a substituent group is selected from halogenatoms.
 3. The lithium-ion battery according to claim 1, wherein inFormula I-1 and Formula I-3: x, y, and z are each independently selectedfrom 0, 1 or 2; and m, n, and k are each independently selected from 1or
 2. 4. The lithium-ion battery according to claim 1, wherein inFormula I-1, R₁, R₃ and R₄ are all hydrogen atoms; and in Formula I-3,at least two of R₁, R₂, and R₃ are hydrogen atoms.
 5. The lithium-ionbattery according to claim 1, wherein in Formula II-1, R₅ is selectedfrom the group consisting of a C₂-C₄ alkylene group, a C₂-C₄ alkenylenegroup, and a C₂-C₄ alkynylene group; and in Formula II-2, R₆ is selectedfrom a C₀-C₁ alkylene group, R₇ and R₈ are each independently selectedfrom the group consisting of a C₂-C₄ alkylene group, a C₂-C₄ alkenylenegroup, and a C₂-C₄ alkynylene group.
 6. The lithium-ion batteryaccording to claim 1, wherein the additive A is selected from one ormore of following compounds:


7. The lithium-ion battery according to claim 1, wherein the additive Bis selected from one or more of the group consisting of succinonitrile,glutaronitrile, adiponitrile, pimelic nitrile, suberonitrile,azelaonitrile, sebaconitrile, undecane dinitrile, dodecane dinitrile,tetramethyl succinate nitrile, methyl glutaronitrile, butenedinitrile,2-pentenedinitrile, hex-2-enedinitrile, hex-3-enedinitrile,oct-4-enedinitrile, oct-4-enedinitrile nitrile,1,2,3-propanetricarbonitrile, 1,3,5-pentanetricarbonitrile, and1,3,6-hexanetricarbonitrile.
 8. The lithium-ion battery according toclaim 1, wherein the electrolyte further contains an additive C, whichis selected from one or more of the group consisting of a cycliccarbonate compound containing a carbon-carbon unsaturated bond, ahalogen-substituted cyclic carbonate compound, a sulfate ester compound,a sultone compound, a disulfonate compound, a sulfite compound, anaromatic compound, an isocyanate compound, a phosphazene compound, anacid anhydride compound, a phosphite compound, a phosphate compound, anda borate compound; and a mass percentage of the additive C in theelectrolyte is 0.01%-30%.
 9. The lithium-ion battery according to claim1, wherein the negative active material in the negative electrode sheetis selected from one or more of the group consisting of soft carbon,hard carbon, artificial graphite, natural graphite, Si, SiOx₂, Si/Ccomposite material, Si alloy, lithium titanate and metal capable offorming an alloy with lithium, 0<x2≤2.
 10. An apparatus, comprising thelithium-ion battery according to claim 1.